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FreeBSD-EN-16:16.hv_storvsc                                     Errata Notice
                                                          The FreeBSD Project

Topic:          Fix SCSI INQUIRY checks and error handling

Category:       core
Module:         hv_storvsc
Announced:      2016-08-12
Credits:        Microsoft OSTC
Affects:        FreeBSD 10.3
Corrected:      2016-07-15 02:29:10 UTC (stable/10, 10.2-STABLE)
                2016-08-12 04:01:16 UTC (releng/10.3, 10.3-RELEASE-p7)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

The Hyper-V storage driver, hv_storsvc(4), uses the SCSI INQUIRY command to
detect the presence of SCSI LUNs.

II.  Problem Description

The hv_storsvc(4) driver assumes 36-byte responses to the INQUIRY command,
which is not always the case.  When a shorter response is received, it can
lead to unexpected behavior.

If the host changes the virtual disk capacity, responses from the host to the
virtual machine guest next command (such as READ CAPACITY or INQUIRY) return
an error with sense data supplied.  The hv_storsvc(4) driver does not check
the error status properly, so the upper SCSI layer treats the command as being
successfully executed, resulting in unexpected behavior.

III. Impact

There are several manifestations of the impact, such as disk hotplug not
working reliably, SMART checks on the disk with 'smartctl -i /dev/da0' can
cause the disk to detach and crash the machine, and online resizing not
working reliably.

IV.  Workaround

No workaround is available, however FreeBSD virtual machines not running in
Hyper-V or Azure are unaffected.

V.   Solution

Perform one of the following:

1) Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.  After which, reboot the
system.

2) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
After which, reboot the system.

3) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-16:16/hv_storvsc.patch
# fetch https://security.FreeBSD.org/patches/EN-16:16/hv_storvsc.patch.asc
# gpg --verify hv_storvsc.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/10/                                                        r302863
releng/10.3/                                                      r303984
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-16:16.hv_storvsc.asc>

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